Vázquez María I, Romero Virgina, Vega Victor, García Javier, Prida Victor M, Hernando Blanca, Benavente Juana
Department of Applied Physics I, Faculty of Sciences, University of Málaga, E-29071 Málaga, Spain.
Department of Physics, Faculty of Sciences, University of Oviedo, E-33007 Oviedo, Spain.
Nanomaterials (Basel). 2015 Dec 5;5(4):2192-2202. doi: 10.3390/nano5042192.
Synthesis of a nanoporous alumina membrane (NPAM) by the two-step anodization method and its morphological and chemical surface characterization by analyzing Scanning Electron Microscopy (SEM) micrographs and X-Ray Photoelectron Spectroscopy (XPS) spectra is reported. Influence of electrical and diffusive effects on the NaCl transport across the membrane nanopores is determined from salt diffusion measurements performed with a wide range of NaCl concentrations, which allows the estimation of characteristic electrochemical membrane parameters such as the NaCl diffusion coefficient and the concentration of fixed charges in the membrane, by using an appropriated model and the membrane geometrical parameters (porosity and pore length). These results indicate a reduction of ~70% in the value of the NaCl diffusion coefficient through the membrane pores with respect to solution. The transport number of ions in the membrane pores (Na⁺ and Cl, respectively) were determined from concentration potential measurements, and the effect of concentration-polarization at the membrane surfaces was also considered by comparing concentration potential values obtained with stirred solutions (550 rpm) and without stirring. From both kinds of results, a value higher than 0.05 M NaCl for the feed solution seems to be necessary to neglect the contribution of electrical interactions in the diffusive transport.
报道了通过两步阳极氧化法合成纳米多孔氧化铝膜（NPAM），并通过分析扫描电子显微镜（SEM）显微照片和X射线光电子能谱（XPS）光谱对其形态和化学表面进行表征。通过在广泛的NaCl浓度下进行盐扩散测量，确定了电效应和扩散效应对NaCl跨膜纳米孔传输的影响，这使得通过使用合适的模型和膜几何参数（孔隙率和孔长度）来估计特征电化学膜参数，如NaCl扩散系数和膜中固定电荷的浓度。这些结果表明，相对于溶液，通过膜孔的NaCl扩散系数值降低了约70%。通过浓度电势测量确定了膜孔中离子（分别为Na⁺和Cl）的迁移数，并且通过比较在搅拌溶液（550 rpm）和不搅拌情况下获得的浓度电势值，还考虑了膜表面浓度极化的影响。从这两种结果来看，进料溶液中NaCl浓度高于0.05 M似乎是忽略扩散传输中电相互作用贡献的必要条件。
